Abstract:

Roasting followed by supercritical fluid CO2 extraction (SFE) was used to produce aromatic soybean oil (ASO). According to the overall odor evaluation, the optimal temperature and time for roasted soybeans with aromatic flavor were 170 ℃ and 30 min, respectively. With increasing particle size of roasted soybean powder, ASO yield increased and the optimal particle size range was 40 － 60 mesh. Orthogonal array design experiments showed that ASO yield first increased and then decreased with increasing extraction temperature and the optimal extraction temperature was 50 ℃; extraction pressure exhibited the same effect on ASO yield as extraction temperature and its optimal value was 25 MPa; ASO yield progressively ascended to the climax appearing at 2.5 h with increasing extraction time. Induction period (IP) and protection factor (PF) were used to evaluate the oxidative stability of ASO. The IP values of ASO and a commercial brand of soybean oil were determined to be 8.93 and 9.47, respectively, which were lower than those of other plant oils determined to be more than 16. The respective additions of BHT and PG at 0.04% level to ASO resulted in an increase of IP value from 8.93 to 12.08 and 18.55 and an increase of PF to 1.353 and 2.077, respectively, thereby indicating much better antioxidant effect of PG on ASO than BHT. ASO added with 0.01% of citric acid exhibited a PF value of up to 2.25, and thus citric acid was a stronger antioxidant for ASO than PG. A PF value of up to 4.14 was observed when 0.01% of citric acid and 0.04% of PG were added to ASO together.

Key words: soybean oil, supercritical fluid extraction (SFE), oxidative stability index (OSI), orthogonal array design, roasting